Various types of microphones and receivers have been used through the years. In these devices, different electrical components are housed together within a housing or assembly. Other types of acoustic devices may include other types of components. These devices may be used in hearing instruments such as hearing aids, personal audio headsets, or in other electronic devices such as cellular phones and computers.
Some microphones use a Micro-Electro-Mechanical Systems (MEMS) transducer that receives sound energy and converts the sound energy into an electrical signal. These microphones may also use Application Specific Integrated Circuits (ASICs) that take the electrical signal from the MEMS transducer and perform post processing on the signal and/or buffering of the signal for the following circuit stages in a larger electronic environment.
The output of the ASIC can be in analog form or in digital form, and the microphones with an ASIC providing digital output are known as digital microphones. In recent years digital microphones have become increasingly popular in portable electronic equipment and in particular in mobile phones.
At the same time, there is also an increased demand for microphones supporting high Acoustic Overload Point (AOP) levels. Higher sound levels mean higher voltage levels at the MEMS output to ASIC. This increase means that MEMS output voltage level can be higher than the supply voltage level of the ASIC, which will consequently create a dynamic range problem, where the ASIC will not be able to handle such high input voltage levels without clipping the signal at the input. Constant clipping of the signal at the ASIC input is not acceptable in a microphone system, because this will reduce dynamic range (DR) of the microphone.
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